LS Dyna

LS Dyna

Hyperelastic material model verification?

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    • aman7
      Subscriber
      Hello,nI am working to model a material using Mooney-Rivlin (MR) model. I have the experimental data. I used the curve fitting tool in ansys to find the coefficients of MR model. Now I want to verify the model with simulation. I made a cylindrical sample of material and I have given it the displacement equivalent to strain in material during experiment so that it gets loaded under same strain rate. Now the Von-Mises stresses I am getting from the simulation are not matching the experimental values as I have used the same experimental data to drive its model. I think conversely it should give similar stress under similar loading. Can anybody help me in this regarding? n
    • peteroznewman
      Subscriber
      nWatch the ANSYS Course video on Hyperelastic curve fitting.nIt describes how to validate the material model results against the experimental data.nThe example uses a unit cube with edge length of 1 m. The model outputs the reaction force for an applied displacement on one face. Since the force acts on a face that has an area of 1 sq. m the force has the same units as Engineering Stress in Pa. Similarly, since the length of the cube is 1 m, the applied displacement is equivalent to Engineering Strain.n
    • aman7
      Subscriber
      nThank you for your reply. The video is informative. But in mean time I get to know that hyperelastic material FEM face problems of shear and volumetric locking. I have seen some videos that suggest using reduced integration. nI don't know how to use reduced integration?n
    • peteroznewman
      Subscriber
      nReduced Integration may be automatically selected by the solver. Read the Solution Output and look for Keyops.nReduced Integration is set by Keyops, often Keyop,2,1. Look in Ansys Help in the Element Library for the element used in your model.n
    • aman7
      Subscriber
      nthe values of KEYOPTs is as:nKEYOPT(2) = 0 for SOLID186 means Uniform reduced integration. How can i use other methods like selective reduced integration?n
    • peteroznewman
      Subscriber
      nSOLID186 is a Quadratic element and has only two choices: Full Integration and Uniform Reduced Integration.nUnder Mesh, set the Element Order to Linear. SOLID185 has four choices for Element Technology.ntKEYOPT(2)nElement technology:nt0 -- nFull integration with n method (default)nt1 -- nUniform reduced integration with hourglass controlnt2 -- nEnhanced strain formulationnt3 -- nSimplified enhanced strain formulationn
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